The present invention relates to the unloading of bulk bags or flexible intermediate bulk containers (FIBCs) used as containers for powdered and particulate materials, and more particularly relates to the unloading of bulk bags fabricated from cloth like material, such as woven polyester material, which is usually sewn in a generally cubical or rectilinear configuration.
Bulk bags made of heavy cloth material have been known in the art for sometime. The bag typically has a central outlet spout at the bottom which is aligned with a discharge unit, for example a conveyer, hopper or the like, into which the material in the bag is intended to be discharged. To discharge material from the bag, the bag is hung in a support frame and the spout is engaged with a discharge unit. The spout is opened and the particulate material flows via gravity through the spout.
It is a characteristic of some particulate materials contained in bulk bags to resist or stop flowing out of the spout when the material remaining in the bag reaches the material's angle of repose or bridges over the spout. Since the bottom of the bag, extending from the spout to the walls, is typically not at angle greater than the material's angle of repose, not all of the material will be discharged through the spout by gravity. The material remaining in the bag after the discharge by gravity often forms a cone shape inside the container. The inner face of this cone shape, formed by the material, extends from the spout in the bottom of the bag upward at an angle to the walls and corners of the bag. The angle of repose at which this cone shape occurs and discharge by gravity ends depends on the physical characteristics of the bulk material involved.
To promote flow and reduce the likelihood of stacking of material along the walls, it is known in the art to use rotatable plate assemblies adjacent the bottom of the bag. The rotatable plates rotate from a substantially horizontal position to an inclined position to push the bottom corners of the bag inward to promote flow towards the central spout. While the rotatable plate assemblies have proven successful in helping promote flow, some materials having a high angle of repose and resistance to flowing freely still tend to stack along the walls and the corners of the bag.
An additional solution, which was developed by the assignee of the present application and is disclosed in U.S. Pat. No. 6,290,098, which is incorporated herein by reference as if fully set forth, provides a flow promotion apparatus for use in conjunction with a bulk bag discharger having a pair of spaced apart mounting brackets, an actuator, a connecting rod and a push bar. The actuator is pivotably connected at one end to one of the mounting brackets. The connecting rod is pivotably connected at one end to the other mounting bracket and pivotably connected at its other end to the piston. The push bar is pivotably coupled at the junction between the actuator and connecting rod, and actuation of the actuator extends the push bar to agitate material along the side walls of the bag.
However, for some materials it is still necessary to provide a better way to promote flow from the bulk bag, especially from the corners.